Stainless Steel Coil Tube for Fan Coil Units — Model JSX-CT Series
1. Product Overview
The JSX-CT Series Stainless Steel Coil Tube (盘管 / Coil Tube) is a precision-engineered heat exchange component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Specifically designed for integration into Fan Coil Units (FCUs) within commercial and residential air conditioning systems, this product represents the culmination of advanced Computer-Aided Design (CAD) methodologies applied to thermal management engineering.
The coil tube assembly serves as the primary heat transfer medium in evaporator and condenser sections of fan coil units, facilitating efficient thermal exchange between the refrigerant circuit and the ambient air stream. By leveraging parametric CAD modeling and Computational Fluid Dynamics (CFD) simulation, the design achieves optimal flow channel geometry, minimizing pressure drop while maximizing heat transfer surface area.
2. Material & Properties
2.1 Base Material
- Primary Alloy: Austenitic Stainless Steel, Grade 304 (UNS S30400) and 316L (UNS S31603)
- Chemical Composition (Grade 304): Carbon ≤ 0.08%, Chromium 18.0–20.0%, Nickel 8.0–10.5%, Manganese ≤ 2.0%, Silicon ≤ 1.0%
- Chemical Composition (Grade 316L): Carbon ≤ 0.03%, Chromium 16.0–18.0%, Nickel 10.0–14.0%, Molybdenum 2.0–3.0%
2.2 Mechanical Properties
| Property | Grade 304 | Grade 316L |
|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 |
| Yield Strength (MPa, 0.2% Offset) | ≥ 205 | ≥ 170 |
| Elongation (% at Break) | ≥ 40 | ≥ 45 |
| Density (kg/m³) | 7,930 | 8,030 |
| Thermal Conductivity at 20°C (W/m·K) | 16.3 | 14.6 |
| Thermal Conductivity at 100°C (W/m·K) | 18.8 | 16.3 |
| Operating Temperature Range (°C) | −196 to +870 | −196 to +870 |
| Corrosion Resistance | Excellent (general atmospheric) | Superior (chloride/marine environments) |
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | 7.0 mm, 9.52 mm (3/8"), 12.7 mm (1/2") — configurable |
| Tube Wall Thickness | 0.5 mm – 1.0 mm (standard); up to 1.5 mm (heavy-duty) |
| Coil Pitch (Center-to-Center Spacing) | 12.7 mm – 25.4 mm (adjustable per thermal load) |
| Number of Rows (Passes) | 2, 3, 4, or 6 rows |
| Coil Length (per Section) | 300 mm – 1,200 mm |
| Fins per Inch (FPI) | 10 – 14 (aluminum fins, hydrophilic coated) |
| Maximum Operating Pressure | 2.5 MPa (design); 4.0 MPa (hydrostatic test) |
| Refrigerant Compatibility | R-410A, R-32, R-134a, R-407C, HFO blends |
| Surface Finish | Electropolished (Ra ≤ 0.4 μm) or passivated |
| Joining Method | TIG (GTAW) welding, orbital or manual; brazing with copper or silver-based alloys |
| Compliance Standards | ASTM A269, ASTM A270, EN 10217-7, GB/T 12771 |
4. Manufacturing Process
4.1 Design Phase
The coil tube design process begins with Computer-Aided Design (CAD) modeling using parametric software (e.g., SolidWorks, CATIA), incorporating thermal load requirements, airflow constraints, and spatial envelope limitations of the target fan coil unit. Computational Fluid Dynamics (CFD) analysis is performed to optimize serpentine tube layout, minimizing flow maldistribution and thermal stratification.
4.2 Production Workflow
- Material Selection & Inspection: Raw stainless steel seamless tubing conforming to ASTM A269/A270 is verified via spectroscopic analysis and dimensional gauging.
- Cut-to-Length: Precision laser cutting or cold shearing to specified tube lengths with tolerance ±0.5 mm.
- Forming & Bending: Numerically controlled (CNC) bending machines form tubes into serpentine or U-bend configurations with controlled bend radii (minimum 3× OD) to prevent ovalization and wrinkling.
- Fin Attachment: High-density aluminum fins are mechanically stamped and expanded onto the tube array, or hydrophilic-coated fins are soldered for enhanced moisture management.
- Welding & Brazing: Header connections are fabricated using Tungsten Inert Gas (TIG) welding under argon shielding. Brazing is performed in a vacuum or nitrogen-atmosphere furnace at 600–700°C using copper-phosphorus or silver-copper filler alloys.
- Surface Treatment: Passivation (citric acid or nitric acid bath) or electropolishing to remove free iron contamination and enhance passive oxide layer integrity.
- Quality Assurance: Hydrostatic pressure testing, dye penetrant inspection (DPI), and dimensional verification per ASME BPVC Section VIII.
5. Applications
- Commercial HVAC Systems: Evaporator coils in ceiling-mounted and ducted fan coil units for office buildings, hotels, and hospitals.
- Residential Air Conditioning: Indoor unit heat exchangers in split-system and multi-split VRF (Variable Refrigerant Flow) configurations.
- Industrial Process Cooling: Precision temperature control in cleanrooms, data centers, and laboratory environments requiring stainless steel corrosion resistance.
- Marine & Coastal Applications: Grade 316L coil tubes deployed in humid, salt-laden environments where chloride pitting resistance is critical.
- Food & Pharmaceutical Processing: Sanitary-grade coil assemblies compliant with FDA and 3-A standards for hygienic cooling applications.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ASTM A269 / A270 | Seamless austenitic stainless steel tubing for heat exchange |
| EN 10217-7 | Welded stainless steel tubes for heat exchangers |
| GB/T 12771 | Chinese national standard for stainless steel seamless tubes |
| ASME BPVC Section VIII | Pressure vessel and heat exchanger construction |
| UL / CE Marking | Electrical safety and conformity for HVAC end products |
| NACE MR0175 | Resistance to sulfide stress cracking (for oil & gas applications) |
7. Unique Selling Points
- CAD-Optimized Thermal Performance: Parametric design and CFD validation ensure ≥15% improvement in heat transfer coefficient (U-value) compared to conventional coil geometries, reducing compressor runtime and energy consumption.
- Superior Corrosion Resistance: Austenitic stainless steel construction eliminates internal corrosion that plagues copper and aluminum alternatives, extending service life beyond 20 years even in aggressive environments.
- Hygienic & Sanitary Grade: Electropolished interior surfaces (Ra ≤ 0.4 μm) prevent microbial colonization, making the coil tube suitable for pharmaceutical, food-grade, and medical air handling applications.
- Refrigerant-Friendly Design: Compatible with next-generation low-GWP refrigerants (R-32, HFO-1234ze), supporting global regulatory transitions toward climate-friendly HVAC systems.
- Customizable Configurations: Modular design allows tailoring of tube diameter, fin density, row count, and coil length to match specific thermal load and spatial constraints.
- Full Traceability: Each production batch is accompanied by mill certificates, material test reports (MTR), and non-destructive testing (NDT) documentation for complete supply chain traceability.
Wenzhou Jixing Metal Materials Co., Ltd. — Leveraging advanced CAD-driven engineering and premium austenitic stainless steel metallurgy to deliver high-performance coil tube solutions for the global HVAC and thermal management industries.